Hydroformylation of 1,5‐Hexadiene Catalyzed by Rhodium Complexes in Supercritical Carbon Dioxide and in Toluene: Effects of Fluorinated Phosphane Ligands and Reaction Conditions

Rhodium‐catalyzed hydroformylation of 1,5‐hexadiene to dialdehydes was investigated in compressed CO 2 and in toluene using different fluorinated phosphane compounds as ligands at a temperature of 60 °C. Product yields depend greatly on the ligand used and, of the ligands examined, tris[3,5‐bis(trifluoromethyl)phenyl]phosphane is the most effective for the production of dialdehydes both in supercritical CO 2 (scCO 2 ) and in toluene. The total yield of the dialdehydes passes through a minimum at about 9 MPa as the CO 2 pressure is increased and increases appreciably as the H 2 pressure in scCO 2 increases. The effect of the syngas (H 2 /CO) and H 2 pressures on the reaction in scCO 2 is different from that in toluene. It has been suggested that scCO 2 promotes the hydroformylation reaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)